| abstract |
PURPOSE: To obtain a gas separating membrane having high separating performance over a long period of time by using arom. polyimide consisting of a specified tetracarboxylic acid component and a specified diamine component in a certain ratio. n CONSTITUTION: A gas separating membrane is made of arom. polyimide obtd. by copolymerizing repeating units (A) of a tetracarboxylic acid component based on biphenyltetracarboxylic acids represented by formula I with repeating units (B) of a diamine component based on 1,4-bis(4-aminophenoxy)benzenes and diaminodiphenyl ethers or 1,3-bis(aminophenoxy)benzenes represented by formula II or III. The molar ratio between the repeating units A:B is 30:70-90:10 and the arom. polyimide has ≥0.5×10 -3 cm 3 /cm 2 .sec.cmHg velocity of permeation of steam. When the gas separating membrane is used, mixed vapor of water and org. matter is easily and efficiently separated over a long period of time and highly concd. vapor of the org. matter is produced. n COPYRIGHT: (C)1990,JPO&Japio |